TPO (thermoplastic olefin) and PVC (polyvinyl chloride) building membranes, in particular roofing membranes, are widely used for waterproofing of structures because of their waterproofness, strength, flexibility and durability.
It would be useful to have a way to provide a membrane with identifying information (i.e., an identifier, such as a unique numeric or alphanumeric code) that remains readable throughout its lifetime. Other information about the membrane (such as its characteristics, customer information, installer, repair records etc.) could then be associated with the identifier (e.g., in a database) and accessed and updated over time, thus facilitating inspection.
Although identifying information might be printed on the outside of a membrane, it would then be at risk of unwanted alteration or removal. In order to aid inspection, it would also be beneficial to be able to read identifying information from membranes that have been incorporated into a structure and are thus invisible or difficult to access.
RFID (Radio Frequency Identification) tags are small, commercially available devices that are capable of electronically storing information and communicating by radio waves. Information can be programmed into a tag and then later read by radio wave interrogation with a suitable RFID reader. RFID tags may be attached to objects and have found various applications, particularly as means of identification. For example, U.S. Pat. Nos. RE 40,145, 7,607,583, 8,579,201, 8,181,580, 8,585,850, 9,340,059, 9,447,547 and 9,476,164 and U.S. Patent App. Pub Nos. 2004/0238623 and 2015/0246504 disclose various applications of RFID tags (such as in credit cards and industrial mats) and related methods of manufacture. Because of their use of radio wave communication, RFID tags, unlike written text or barcodes, can be read when not in line of sight.
Although it might in principle be possible to affix RFID tags to the outside of TPO or PVC building membranes, the tags could then be subject to unwanted removal and would be exposed to potential damage, in particular from the elements or physical impact. It would thus be desirable to embed RFID tags in the membranes. In this way the tags would be protected from removal or environmental damage, but would still be readable (by radio wave communication).
In general, TPO or PVC roofing membrane is constructed of three layers: a core layer of TPO or PVC, a polyester scrim to provide strength and structure to the sheet, and a cap layer of TPO or PVC. Weather protection is provided by the cap layer, which is thicker than the core/scrim layer and contains additives to improve weather resistance and to provide a long life. Examples of such additives are titanium oxide (to provide desired reflective properties) or anti-UV agents that extend the membrane's life on the roof.
During manufacturing, TPO & PVC roofing membranes are subject to intense heat (over 400° F.) and dynamic forces (e.g., due to passage of the membrane through calendar rollers). Such conditions have the potential to compromise the readability of non-specialized RFID tags.
U.S. Pat. No. 8,284,028 and German Patent No. DE 20200801065 disclose methods of incorporating RFID tags into bituminous roofing products. Although in these methods the RFID tags are applied to hot bitumen and thus must endure elevated temperatures, the thermal and mechanical challenges encountered during the manufacturing of TPO or PVC membrane are greater. This U.S. patent is incorporated herein by reference in its entirety for all purposes within this application.